1. Field of the Invention
The present invention relates to a bonding apparatus, and more particularly, to a substrate bonding apparatus for bonding substrates to each other during the manufacturing of a liquid crystal display (LCD) device.
2. Discussion of the Related Art
In response to an increased demand for various display devices, flat panel type displays such as liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed. In particular, with characteristic advantages of high resolution, lightness, thinness, and low power consumption, LCD devices has been commonly used as a mobile image display device to replace cathode ray tube (CRT) devices. In addition, LCD devices are commonly used for monitors of notebook computers, and as monitors of computers and televisions. In order to use LCD devices as general image displays, operational characteristics of low weight, thin profile, and low power consumption must be maintained.
A method for manufacturing an LCD device may be divided into two catagories: liquid crystal injecting and liquid crystal dispensing. The liquid crystal injecting type includes steps of forming a sealant pattern on a first substrate to form an injection inlet, bonding the first substrate to a second substrate in a vacuum state, and injecting liquid crystal material through the injection inlet. The liquid crystal dispensing method, which is disclosed in Japanese Patent Application Nos. 11-089612 and 11-172903, includes steps of dispensing liquid crystal material on a first substrate, arranging a second substrate over the first substrate, and moving the first and second substrates, thereby bonding the first and second substrates to each other in a vacuum state. Compared to the liquid crystal injection method, the liquid crystal dispensing method is advantageous in that various steps, such as forming a liquid crystal material injection inlet, injecting the liquid crystal material, and sealing the injection inlet can be omitted.
FIG. 1 and FIG. 2 illustrate a related art vacuum bonding device, to which the prior art liquid crystal dispensing method is applied. The related art vacuum bonding device includes a frame 10 forming the exterior, a stage part 22 and 21, a sealant dispenser (not shown), a liquid crystal dispenser 30, a chamber part 32 and 31, a chamber moving system, a stage moving system, an alignment system and a vacuum pump 60.
At this time, the stage part is divided into lower and upper stages 22 and 21, and the sealant dispenser and the liquid crystal dispenser 30 are provided at a side of location where a bonding process is carried out. The chamber part is divided into lower and upper chamber units 32 and 31 that are to be combined. Also, the chamber moving system includes a driving motor 40 that is driven to selectively move the lower chamber unit 32 to a location at which the bonding process is carried out, or to a location at which the dispensing of the sealant or the liquid crystal occurs. The stage moving system includes another driving motor 50 that is driven to selectively move the upper stage 21 to the upper or lower part. The vacuum pump 60 is connected to a tube that is connected to the inside of the upper chamber unit 31 so as to provide an air inhalation to the inside of the upper chamber unit 31 for maintaining the upper chamber unit in the vacuum state. The alignment system includes an align camera 70 that checks an alignment state between the substrate 52 (hereinafter, referenced as “second substrate”) fixed to the upper stage 21, and the substrate 51 (hereinafter, referenced as “first substrate”) fixed to the lower stage 22. Also, the upper chamber unit is provided with a through hole 31a that checks the alignment state between the substrates through the align camera 70.
A method for manufacturing the LCD device with the related art device for fabricating the substrates will be explained as follows.
First, the second substrate 52 is loaded to the upper stage 21, and is fixed thereto. Then, the first substrate 51 is loaded to the lower stage 22, and is fixed thereto. In this state, the lower chamber unit 32, having the lower stage 22, is moved by the chamber moving system 40 to a processing location for depositing the sealant and dispensing the liquid crystal, as shown in FIG. 1. Upon completing the deposition of the sealant and the dispensing of the liquid crystal, the lower chamber unit 32 is moved to a processing location at which the substrates are bonded to each other, as shown in FIG. 2. After that, the lower and upper chamber units 32 and 31 are assembled together by the chamber moving system 40 to form a vacuum tight seal, and the vacuum pump 60 is driven so as to make the vacuum state.
The upper stage 21 is moved downwardly, and is positioned at a location for aligning each substrate 51 and 52. Then, the align camera 70 checks each align mark of the first and second substrates 51 and 52, respectively fixed to each stage, through a hole provided in the upper chamber unit 31 and a through hole 21a provided in the upper stage 21. At this time, displacement of each substrate is checked by the align camera 70, and then is calculated to a numeral value. Then, each substrate is aligned in controlling the stage moving system according to the numeral value.
On completing the alignment of the substrates, the upper stage 21 is moved further downward by the stage moving system 50. The second substrate 52 fixed to the upper stage 21 is contacted to the first substrate 51 fixed to the lower stage 22, and then a constant pressure is applied to the substrates, thereby bonding the substrates to each other.
However, the related art bonding device of the LCD device has the following problems.
As the align camera comes close to each align mark of the substrates, the align accuracy is improved in that the align camera can exactly check the align state of the substrates. However, in the related art bonding device, a distance (L1) is maintained between the lens of the align camera and an external surface of the upper chamber unit, so that it is hard to exactly check the align state of each substrate. Especially, in a case of the large-sized LCD device, the align accuracy is deteriorated in that the distance becomes great between the lens of the align camera and the external surface of the upper chamber unit. Also, a distance (L2) is generated between an internal surface of the upper chamber unit and the align mark of the substrate, thereby deteriorating the align accuracy. Furthermore, only one align camera is used for checking the align marks of each substrate in the related art bonding device, thereby increasing processing time.
If the align camera obtaining high accuracy is not used for checking the align marks of each substrate in the large-sized LCD device, it is hard to exactly align each substrate. Accordingly, the alignment system having a structure that is suitable for manufacturing the large-sized LCD device has been actively studied and is needed for large-sized LCD devices.